This invention relates generally to devices for occlusion of ducts, and more particularly concerns an artificial sphincter for use inside a human or animal body as a substitute for a natural sphincter, and whose purpose is to contract a bodily opening or duct and release the same for passage of fluid material therethrough.
Occlusive muscles, such as the sphincter, perform various functions in the human or animal body. One of these muscles, the urinary sphincter, controls the passage of urine from the bladder through the urethral duct. When the urinary sphincter malfunctions, is surgically removed or is impaired for other reasons, control of the flow of urine through the urethra is lost thereby producing a situation of incontinence. Various drainage devices, diaper type collectors and urinal attachments have been used to assist persons having urinary incontinence. Those items, while helping make life more routine for such persons, do not affect the source of the problem, namely the lack of muscular control of the urethra. Lately, however, a number of solutions have been proposed as substitutes for the natural sphincter, to control the flow of urine through the urethral duct, thereby eliminating the need for extra urinary attachments or assists.
A pneumatic sphincter was conceived by Dr. Orvar Swenson by 1956 (Annals of Surgery, Vol. 144, No. 3, Sept. 1956). In that device, an inflatable cuff surrounds the urethra such that voluntary inflation of the cuff prevents the escape of urine through the urethra. Deflation of the cuff opens the urethra to permit bladder emptying. Such a device is implanted outside of the urinary system, however, to prevent infection. Additionally, means for injecting air into the inflatable cuff at periodic intervals is often impractical and cumbersome and may be inconvenient for the user.
In 1972 Dr. Swenson proposed another device which under mechanical control would successfully produce urinary control (Journal of Pediatric Surgery, Vol. 7, No. 5 (Oct-Nov.), 1972). This latest mechanical device of Dr. Swenson offers a number of significant features that results in a very practicable and advantageous product. Following are some of the noteworthy features:
1. Although implanted inside a human or animal body, the mechanical sphincter is outside the urinary system, thereby eliminating or reducing the possibility of infection;
2. The control mechanism is activated by pressure applied through the skin to tighten and release the device;
3. Pressure on the skin over the control fully releases urethral compression to provide a completely unobstructed urethra;
4. The device is implanted completely under the skin; and
5. Pressure on the urethra produced by such a device does not cause stricture or necrosis.
This type of device not only successfully occludes the urethral duct to prevent escape of urine and releases the duct to allow urine flow, but also is conveniently and voluntarily operable by the person having need for such a device. While the advantages of the artificial mechanical sphincter proposed by Dr. Swenson are highly commendable, there are a few shortcomings in its design and function which have been noted.
To occlude the urethral canal the sphincter includes a control mechanism to tighten the diameter of a coil or torus circumferentially located about the urethra. In operation the control mechanism incrementally tightens the coil by voluntary pressure by the user until escape of urine is prevented. However, there is no limit to the tightening level of the control mechanism so that excessive tightening of the coil is permitted which would inflict damage to the urethra. Excessive tightening could be problematical especially in situations where the device is implanted in children, for example. Another problem involves the adjustment of the sphincter after it has been implanted in a body. For instance, after a period of time and use of the sphincter some dribbling may occur. Further tightening by the control mechanism may be uncomfortable or damage the urethra canal. To adjust the tightening coil to overcome this problem often requires an additional surgical or hospital visit so that the surgeon can gain access to the implanted sphincter to perform the necesary adjustments.
Another artificial sphincter is disclosed in British Pat. Specification No. 1,174,814. That spincter includes a pneumatically, hydraulically, mechanically or electrically operable occluding body directly or indirectly connected with operating means for causing movement of the body to close or release the duct.